I have a 93 22re 4runner with over 200k on it. For the last little while, lets say few months it has been having good days and bad days performance. Somedays it seems to run down the highway very good and other days not so good. Now mind you on the bad days it still get from point A to B but whos happy knowing that there truck has the potential to run better. Lately i have noticed and it may have always been like this, but on a good days and after it is well warmed up it idles very smooth at around 1000 rpm and is very quite, too quite almost for a manual trans. On a bad day however it idles lower at around 700 rpm and it fluctuates +/- 100rpm and the runner shakes and it is rather loud and rough sounding. I have new cap, rotor, wires, plugs, oil, tailpipe, relatively new exhaust. Does anyone know why my runner acts like this? I tried searching the irradicate idle threads but they dont seem to be the same.

 

have you treid the rough idle tests in the fsm? it could be bad thermostat or any part of the egr system.

 

Vacuum leaks? Air Intake Tube leaking? Any air getting into the intake that isn't going past the AFM is air volume that is NOT being measured by the AFM.

Also make sure the TPS is properly adjusted and functioning within spec.

MIke in AR

 

Like he said...

Sorry to hi-jack, but it's storytime!

I saw a mid-'90s Miata come through the shop one day that had a terribly ragged idle, and the customer had put about $500 into repair parts, to no avail. Me and Rob (the greatest auto tech i've ever seen) came to the conclusion that it might be a problem of unmetered air. We traced the intake piping from the intake, and asked the guy what maintenance he had done to it before the problem, and he had a belt replaced, and other than that, just regular maintenance.

Now I GUESS the guy that had put on the belt didn't have the right belt in stock, so he used a slightly larger belt and just adjusted with the tensioner and the power steering pump, which WOULD'VE worked had the pulley (that he slacked extremely to accomodate the larger belt) not been positioned RIGHT under the section of plastic air duct right before the throttle body. We noticed that when the hood was up, there was a faint odor of melting plastic, so we investigated for about 20 minutes, and then saw the pulley pressed into the intake duct, and it had burned a hole in it. After some JB Quik-Weld, and a new belt, it purred like a kitten, and the customer was out about $30 for a permanent fix.

So check out your vacuum system, and look for a post MAF leak (un-metered air).

I like telling stories.

 

my 90 4runner which has 236000 miles does that all the time it rumbles at idle when you give mine a little gas it stops but i would like to kno how to fix that to b/c its anoying

 

this may sound rather dumb but what is the best way to check for vacum leaks. I pop the hood and look at them and they LOOK alright but that cant be the most accurate way to check.

 

Mechanics stethescope. Listen for hissing sounds around any of the vacuum lines.